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Chem Unit 3 > 3.3 The p-block > Flashcards

3.3 The p-block Flashcards

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1
Q

why are they called the p-block elements?

A

each of the p-block elements have their outer e- in p orbital

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2
Q

amphoteric behaviour??

A

an amphoteric species can act as both an acid & a base

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3
Q

which 2 p-block elements have amphoteric behaviour??

A

Al/Al^3+
Pb/Pb^2+

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4
Q

what is the chemical eqn for rctn bet aluminium oxide and sulfuric acid?

A

Al2O3 + 3H2SO4 -> Al2(SO4)3 + 3H2O

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5
Q

chemical eqn for rctn bet aluminium oxide & sodium hydroxide??

A

Al2O3 + 2NaOH + 3H2O -> 2NaAl(OH)4

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6
Q

chemical rctn bet lead oxide & hydrochloric acid??

A

PbO + 2HCl -> PbCl2 + H2O

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7
Q

chemical rctn bet lead oxide & sodium hydroxide?

A

PbO + NaOH + H2O –> NaPb(OH)3

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8
Q

inert pair effect??

A

tendency of electrons in the outer s orbital to remain unionised and unshared used to explain increasing stability of oxidation states that are 2 less than the grp valency for grps 3,4&5

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9
Q

describe how the stability of oxidation states changes down grp 3

A

in grp 3 stability of 1+ oxidation state increases down the grp
the Tl+ ion is much more common than the Tl3+ ion, at top of grp Al+ ion is v rare due to its instability hence Al3+ ion is more common

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10
Q

describe how stability of oxidation states changes down grp 4??

A

in grp 4 stability of 4+ oxidation state reduces down grp whilst stability of 2+ oxidation state increases down grp

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11
Q

describe how stability of oxidation states changes down grp 5??

A

in grp 5 stability of the 5+ oxidation state reduces down the grp whilst stability of the 3+ oxidation state increases down the grp

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12
Q

describe structure & bonding in Al2Cl6

A

aluminium hexachloride Al2Cl6 is a donor-acceptor dimer, made up of 2 separate identical molecules linked together by 2 dative bonds. 2 atoms of chlorine share their lone pair of electrons with 2 atoms of aluminium to form the dative bonds

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13
Q

describe structure & bonding of NH3BF3

A

NH3BF3 is a donor-acceptor compound there is a dative coordinate bond formed bet nitrogen & boron atoms where nitrogen supplies both electrons for the covalent bond

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14
Q

describe the structure of cubic boron nitride??

A

the cubic form of boron nitride consists of alternately linked boron & nitrogen atoms structure is tetrahedral bond network similar to carbon atoms in diamond, the lone pair of electrons on nitrogen are accepted by boron to give this giant 3D covalent lattice

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15
Q

decribe structure of hexagonal boron nitride??

A

hexagonal boron nitride has layered structure similar to graphite, layers form a 2D giant covalent network, alternate boron & nitrogen atoms link together forming hexagonal rings in thin layers which are held by weak intermolecular forces

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16
Q

explain which boron nitride structure is suitable to be used as lubricant??

A

the hexagonal boron nitride structure as week intermolecular forces bet layers mean they can slide suitable for use as a lubricant

17
Q

identify the reducing agent in following rctn: CuO + CO –> Cu + CO2

A

Cu2+ –> 0 reduced
C2+ –> 4+ oxidised
reducing agent is carbon monoxide

18
Q

chem eqn for rctn bet PbO2 & HCl?? identify oxidising agent

A

PbO2 + 4 HCl –> PbCl2 + 2H2O + Cl2 oxidising agent: Pb(IV)/Pb4+

19
Q

describe general acid-base behaviour trend of grp 4 oxides??

A

acidity of grp 4 oxides decreases as u go down grp oxides towards the bottom are more basic however they dont completely lose their acidic character so are described as amphoteric

20
Q

explain acid-base properties of CO2 and PbO in relation to their position in grp 4??

A

carbon is at top of grp 4 so CO2 is acidic in nature can react w/ bases
lead is towards the bottom of grp4 do lead oxide is amphoteric in nature reacting w/ acids and bases

21
Q

compare rctns of CCl4, SiCl4 & PbCl2 w/ water

A

CCl4 does not react w water
SiCl4 reacts violently w water
PbCl2 is partially soluble in cold water but more soluble in hot water

22
Q

why does CCl4 tend not to react w/ water??

A

for rctn to take place oxygens lp from water need to bond to carbon in CCl4, rctn doesnt occur: chlorine atoms are very bulky and carbon atom is very small so hard for oxygen to get near carbon atom, a lot of repulsion bet various lps as the oxygen atom gets close to chlorine atoms making transition state very unstable, there is not a convenient empty orbital for the oxygen to bond to on carbon atom

23
Q

how is SiCl4 able to react w water??

A

the silicon atom is relatively big so there is space for the oxygen atom on water to attack the silicon atom, silicon also has empty 3d orbitals which can accept a lone pair of e-s from the oxygen atom

24
Q

explain how PbCl2 reacts with water??

A

PbCl2 has a lot of ionic character and can be thought of as ionic in reaction w water, PbCl2 is slightly soluble in cold water but much more soluble in hot water

25
Q

chemical eqn for rctn of SiCl4 w water|??

A

SiCl4 + 2H2O –> SiO2 + 4 HCl

26
Q

chem eqn for rctn of Pb2+ ions w OH- ions??

A

Pb2+ + 2OH- –> Pb(OH)2
Pb(OH)2 dissolves in excess OH-: Pb(OH)2 + 2OH- –> [Pb(OH)4]2-

27
Q

chem eqn for rctn of Pb2+(aq) w/ Cl- ions??

A

Pb2+ + 2Cl- –> PbCl2
with excess Cl-: PbCl2 + 2Cl- –> [PbCl4]2_

28
Q

chem eqn for rctn of Pb2+(aq) ions w I- ions??

A

Pb2+ + 2I- –> PbI2

29
Q

disproportionation rctn??

A

a rctn in which a species simultaneously undergoes oxidation & reduction to form two diff prods

30
Q

chem eqn for disproportionation rctn that chlorine undergoes w/ cold sodium hydroxide??

A

2NaOH + Cl2 –> NaClO + NaCl +H2O

31
Q

chem eqn for the disproportionation rctn that chlorine undergoes w/ warm sodium hydroxide?

A

6NaOH + 3Cl2 –> NaClO3 + 5NaCl + 3H2O

32
Q

chem eqn for disproportionation rctn that chlorine undergoes w/ water??

A

Cl2 + H2O -><- 2H+ + Cl- + ClO-

33
Q

why are chlorine and chlorate ions used in water treatment??

A

they kill bacteria which makes water safe, this is a result of their oxidising power

34
Q

how do sodium chlorid & sodium fluoride rct w/ conc sulfuric acid??

A

chlorides and fluorides are not oxidised by sulfuric acid:
NaCl + H2SO4 –> NaHSO4 + HCl
NaF + H2SO4 –> NaHSO4 + HF

35
Q

how do bromide ions rct w/ conc sulfuric acid??

A

bromide ions can reduce conc sulfuric acid:
2Br- + H2SO4 + 2H+ –> Br2 + SO2 + 2H2O

36
Q

how do iodide ions rct w/ conc sulfuric acid??

A

iodide ions are stronger reducing agents than bromide ions:
8I- + H2SO4 + 8H+ –> 4I2 + H2S + 4H2O

Chem Unit 3 (9 decks)

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